Children with high everyday levels of a protein released into the blood in response to infection are at greater risk of developing depression and psychosis in adulthood, according to new research which suggests ...

Young lovers walking down the aisle may dream of long and healthy lives together, but close friends in the wedding party may have a better sense of whether those wishes will come true, suggests new research ...

A new study of identical twins has found that early reading skill might positively affect later intellectual abilities. The study, in the journal Child Development, was conducted by researchers at the University of Edinbu ...

New research confirms why some people suffer from the winter blues while others get through the winter without any problems. A longitudinal study from a group of researchers from the University of Copenhagen has found that ...

Low levels of vitamin D have been linked to depression, according to UT Southwestern Medical Center psychiatrists working with the Cooper Center Longitudinal Study. It is believed to be the largest such investigation ever ...

(Medical Xpress)—Reading-impaired young children have higher levels of the metabolites glutamate and choline in their brains, and these higher levels continue to be indicative of difficulties in developing ...

In the constant battle to lose inches or at least stay the same, we reach for the diet soda. Two studies presented June 25 and 27 at the American Diabetes Association's Scientific Sessions in San Diego suggest this might ...

Debunking the myth of the "mean girl," new research from the University of Georgia has found that boys use relational aggression—malicious rumors, social exclusion and rejection—to harm or manipulate ...

(Medical Xpress)—Want a good night's sleep? Be positive – consistently. Although happiness is generally good for sleeping, when a person's happiness varies a lot in reaction to daily ups and downs, sleep suffers, reports ...

Exceptional spatial ability at age 13 predicts creative and scholarly achievements over 30 years later, according to results from a new longitudinal study published in Psychological Science, a journal of the Association for Ps ...

All fat is not created equal. Unsightly as it is, subcutaneous fat, the fat right under the skin, is not as dangerous to overall health as visceral fat, the fat deep in the belly surrounding vital organs.

Exposure during pregnancy to flame retardant chemicals commonly found in the home is linked to lower birthweight babies, according to a new study led by researchers at the University of California, Berkeley's School of Public ...

Students who date in middle school have significantly worse study skills, are four times more likely to drop out of school and report twice as much alcohol, tobacco and marijuana use than their single classmates, ...

(Medical Xpress) -- Douglas Gentile says his own research has found both positive and negative effects from playing video games. And the Iowa State University associate professor of psychology cites examples of both in a ...

Longitudinal study

A longitudinal study is a correlational research study that involves repeated observations of the same items over long periods of time — often many decades. It is a type of observational study. Longitudinal studies are often used in psychology to study developmental trends across the life span, and in sociology to study life events throughout lifetimes or generations. The reason for this is that unlike cross-sectional studies, longitudinal studies track the same people, and therefore the differences observed in those people are less likely to be the result of cultural differences across generations. Because of this benefit, longitudinal studies make observing changes more accurate and they are applied in various other fields. In medicine, the design is used to uncover predictors of certain diseases. In advertising, the Communicus System, the design is used to identify the changes that advertising has produced in the attitudes and behaviors of those within the target audience who have seen the advertising campaign.

Because longitudinal studies are observational, in the sense that they observe the state of the world without manipulating it, it has been argued that they may have less power to detect causal relationships than do experiments. But because of the repeated observation at the individual level, they have more power than cross-sectional observational studies, by virtue of being able to exclude time-invariant unobserved individual differences, and by virtue of observing the temporal order of events.

Longitudinal studies allow social scientists to distinguish short from long-term phenomena, such as poverty. If the poverty rate is 10% at a point in time, this may mean that 10% of the population are always poor, or that the whole population experiences poverty for 10% of the time. It is not possible to conclude which of these possibilities is the case using one-off cross-sectional studies.

Types of longitudinal studies include cohort studies and panel studies. Cohort studies sample a cohort, defined as a group experiencing some event (typically birth) in a selected time period, and studying them at intervals through time. Panel studies sample a cross-section, and survey it at (usually regular) intervals.

A retrospective study is a longitudinal study that looks back in time. For instance a researcher may look up the medical records of previous years to look for a trend.